This invention relates to a device for monitoring the activity of a person travelling on a transportation vehicle and notifying that person of a specified pattern and frequency of their activity or inactivity, in order to reduce the risk of them developing deep vein thrombosis.
The present invention finds a particular use in the prevention of deep vein thrombosis (DVT), which is often caused by extended periods of inactivity, and it will be primarily described with reference thereto.
Deep vein thrombosis is a condition resulting from the lack of blood flow in the veins and the condition is related primarily, but not exclusively, to the legs. Blood flow tends to slow down or stop when there is prolonged inactivity, especially when seated, as would happen on a plane or any long journey in a cramped space. More specifically deep vein thrombosis occurs when a clot forms in the deep veins within the calf or thigh muscles. It is usually a spontaneous condition that occurs in people especially at risk, such as those with heart disease, those who smoke or consume alcohol and those that are generally overweight.
Any period of prolonged inactivity can generally trigger the condition and medical research suggests that those over forty years of age are at ever increasing risk. Warning signs are pain and tenderness in the leg muscles, redness and swelling of the skin. If the blood clot moves to the lung (a pulmonary embolus), then breathing difficulties can occur. A clot travelling on to the heart can cause death or if it travels to the brain a stroke is a possibility. There are well-documented cases of people suffering from this condition during long haul plane journeys and there have been some deaths attributed to DVT. In recent times a number of airline passengers have taken legal action against airline companies relating to this condition, and some companies are now putting warnings on their tickets.
The more cramped the condition, such as would occur in the economy class area of a plane, the more likely a person is to suffer from DVT, but recent medical research shows that the condition can occur to any class of traveller who does insufficient exercise.
It is to be expected that on a long haul flight lasting several hours that people will sleep for extended periods of this time. This cannot be prevented on an individual basis and this is where a problem may arise. Furthermore, due to the cramped conditions, people may at other times, for one reason or another remain essentially motionless. This inactivity reduces the blood flow in the legs and the potential problem of DVT becomes a factor.
Regular use of the legs during a journey dramatically reduces the risk of DVT. However, the transportation operators have no way of ensuring that suitable exercise is done by their passengers, despite the fact that the health and safety of those passengers is at least partially the airline operator's responsibility. The problem of DVT is not limited to airline travel, but is also encountered in other forms of transport such as cars, coaches and trains wherein prolonged periods of sedentary inactivity occur, usually in confined areas.
At present, the onus may be on travel operators to ensure that their passengers do not get DVT. However, the present type of traveller on long haul flights will clearly fit many of the conditions associated with DVT and as such can expose the travel operators to significant risk of negligence claims.
Previous attempts have been made to monitor the movement of patients such as those described in U.S. Pat. No. 5,941,836, U.S. Pat. No. 6,646,556, U.S. Pat. No. 4,536,755, U.S. Pat. No. 5,523,742, U.S. Pat. No. 4,064,368 and U.S. Pat. No. 6,445,298. None of these are designed for or suitable for use by passengers on transportation vehicles because they are large, cumbersome, suitable only for lying down and/or unable to distinguish relevant exercise movement from background movement caused by incorrect activity or the motion of the transportation vehicle.